Glyphosate, the world’s most widely used herbicide, annually provides a positive contribution to reducing global carbon dioxide equivalent (CO2e) emissions arising from agricultural production of between -32.17 billion kg and -45.18 billion kg, equal to taking between 21.3 and 29.9 million cars off the road each year.  This is the primary conclusion of a new peer reviewed paper recently published in the journal GM Crops & Food.  This positive contribution stems from glyphosate’s instrumental role in facilitating a shift in farming practices that are tillage-based into conservation tillage systems based on reduced and no tillage, notes the paper’s author, agricultural economist Graham Brookes.

 

A new peer-reviewed paper recently published in the journal GM Crops & Food points to the key role of glyphosate, the world’s most widely used herbicide, in reducing carbon dioxide emissions from agriculture. The paper calculated the annual global CO2e emissions from the manufacture, distribution, and farm level use of glyphosate.  It then estimated the annual contribution of glyphosate to reducing CO2e emissions via its facilitating role in the adoption of conservation tillage systems based on reduced and no tillage in which these tillage practices lead to CO2e reduction via additional soil carbon storage and reduced fuel use in soil preparation.

 

Total annual global use of glyphosate is 749.27 million kg of active ingredient, applied to 646.11 million (spray) hectares.  The CO2e emissions generated from the manufacture, distribution, and application of glyphosate in global agriculture is annually 9.76 billion kg. 

 

Calculating the annual contribution of glyphosate to reducing CO2e emissions via its facilitating role in the adoption of reduced and no tillage farming systems first required a detailed literature review to identify the evidence about emissions after adoption of conservation tillage practices, soil organic carbon levels and other possible emissions such as nitrous oxide (N2O) relative to conventional tillage practices.  This review provided the evidence for setting assumptions for calculating emission savings associated with the adoption of conservation tillage practices (see below) and the evidence for confirming the facilitating role of glyphosate in the adoption and maintenance of no till and reduced till-based conservation tillage practices.    

 

The total global combined annual fuel and soil carbon retention related CO2e emissions of conservation tillage was estimated to be a net reduction of -138.2 billion kg CO2e.  This compares with +41.47 billion kg CO2e emissions if this area had been ploughed with conventional tillage practices.  Therefore, conservation tillage practices provide a net reduction in combined annual fuel and increased soil carbon retention related emissions of -179.67 billion kg CO2e relative to a conventional plough-based alternative production system.

 

The total global combined annual fuel and soil carbon retention related CO2e emissions of conservation tillage attributable to glyphosate was estimated at a net reduction of -41.93 billion kg CO2e (equal to 30.6% of the total carbon storage associated with conservation tillage practices worldwide).  This compares with +13.01 billion CO2e emissions if this area had been ploughed, providing a net reduction in combined fuel and soil carbon related emissions attributable to glyphosate of -54.94 billion kg CO2e annually or the equivalent of taking 21.8 million cars off the road each year. 

 

After taking into consideration the CO2e emissions generated from the manufacture, distribution and application of glyphosate in global agriculture (9.76 billion kg), the net annual global impact of glyphosate use is providing a positive contribution to reducing global CO2e emissions arising from agricultural production of between -32.17 billion kg and -45.18 billion kg, equal to taking between 21.3 and 29.9 million cars off the road each year. 

 

A noteworthy feature of the analysis is the dominance of the main grain and oilseed producing and exporting countries of North and South America in the adoption of conservation tillage practices and associated CO2e emission reduction as well as being the countries where the highest concentration of glyphosate use takes place.  These countries account for 65% of global glyphosate use (in terms of active ingredient use), 72% of global CO2e emission reduction associated with conservation tillage practices and 79% of the share of these CO2e emissions reduction attributable to glyphosate use.  This dominance of the main grain and oilseed exporting countries of North and South American countries is also strongly associated with the widespread adoption of GM HT crops tolerant to glyphosate. 

 

Graham Brookes is an Agricultural Economist with PG Economics, UK.  He has more than 35 years’ experience of analysing the impact of technology use and production systems in agriculture and has authored many papers in peer reviewed journals on the impact of regulation, policy change and new technology adoption. He is a member of the Science for Sustainable Agriculture advisory group.